Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$218.95	3.215%	$225.9892	$225.99	$226.00	$226.00
Purchase #2	$175.50	3.667%	$181.9356	$181.94	$181.95	$181.90
Purchase #3	$43.79	3.821%	$45.4632	$45.46	$45.45	$45.50
Purchase #4	$30.45	10.291%	$33.5836	$33.58	$33.60	$33.60
Purchase #5	$10.42	13.295%	$11.8053	$11.81	$11.80	$11.80
Purchase #6	$74.47	10.754%	$82.4785	$82.48	$82.50	$82.50
Purchase #7	$40.53	13.367%	$45.9476	$45.95	$45.95	$45.90
7 purchase totals =	$594.11		$627.2030	$627.21	$627.25	$627.20